1. Field of the Invention
This invention relates to the field of vehicle and track systems of the type wherein the vehicle is supported on an elongated track and has a drive wheel for cooperation with a rotating drive shaft extending along and parallel to the track. Systems of the indicated type are particularly useful for moving work pallets from station to station as various assembly, machining, processing or test operations are performed on articles supported thereon. Moreover, systems of the indicated type are capable of operating with a non-synchronous transfer load (i.e., the vehicles can move independently of each other), and with a track system that comprises angle turns or elevators to transport the articles.
2. Description of the Prior Art
There have been provided vehicle and track systems in the prior art of the type disclosed herein which are particularly suitable for high speed movement of articles from one precise position to another. In this type of system, in order to operate at relatively high speed during transport, a speed control means for cooperation with the vehicle drive wheel must be utilized. Also, the drive shaft must be mounted for rotation parallel to the movement of the vehicle and the vehicle must be retained on the track in a manner to prevent the vehicle from disengaging from the track at high rates of speed. Also, these systems must be designed to permit vehicles to approach and contact a vehicle in front thereof and there must be provided a control device to cooperate with the drive wheel to effect dense accumulation of vehicles along the track system.
U.S. Pat. Nos. 423,872 issued to Judson and 4,036,148 issued to Jones et al exemplify prior art vehicle track systems having a drive wheel, a drive shaft and a track connected in cooperation therewith to provide forward travel of a vehicle therealong. U.S. Pat. No. 3,818,837 issued to Jacoby et al exemplifies prior art vehicle and track systems which are provided with a speed control means on their front ends for cooperation with a cam on the rear end of the next vehicle on the track system to effect dense accumulation of vehicles along the system.
A problem encountered with vehicle and track systems of the prior art is the location of the shaft directly beneath the vehicle whereby there is interference with any process to be performed from below the vehicle.
Another problem encountered with the prior art systems is that the vehicle is either not self-supporting independently on the drive shaft whereby the drive wheel is affected by either light or heavy loads because of the force applied from the drive wheel to the drive shaft.
Another problem of the prior art systems wherein the vehicle is spring-loaded to the drive shaft directly beneath it is that while the vehicle is restrained on the track, it cannot be removed from the track without disassembling a track section.
Another problem with the prior art systems wherein a speed control device is located at the front end for cooperation with the rear end of the next vehicle to achieve dense accumulation, is that the vehicle cannot be run in the reverse direction and still maintain a speed control means in cooperation with the vehicle in that backwards direction.
Another problem with the prior art systems is that they employ mechanisms to effect dense accumulation of vehicles along the system which do not maintain a precise distance between the accumulated vehicles and in the accumulation position they maintain the angular position of the drive wheel at 0.degree. when cooperating with the next vehicle on the track system thereby resulting in "hunting" or oscillating of the vehicle.